Oh good at least we are on the right track. A quick reading of the error messages and source code suggests that gcs_test doesn’t make use of the GALERA_UNIT_TEST_LIBSglobal variable which we edited earlier to include the atomic library.

Could you try editing line 87 in the gcs/src/CMakeList.txt file:

MariaDB/galera

So that it becomes:

target_link_libraries(gcs_test gcs gcomm atomic)